How to send response from class object promise to controller in nodeJS

Question

I have a question. I am using a NodeJS app divided in three main parts

Data access object Here, I created a function that make the direct interaction with the database only in this file.

const { response } = require('express'); const db = require('../connection/db.js');

/* Export */ module.exports = { // Insert User insertUser: (parameters) => { const sqlStatement = 'INSERT INTO users SET ?'; return new Promise((resolve, reject) => { db.query(sqlStatement, parameters, (error, response) => { if (error) { return reject(error); } return resolve(response); }) }) } }

Object class In this class I will make the validation, and create the method with arguments, then implement the data access object insertUser.

 const db = require('../dataAccessObject/dao.js');

class User { constructor (fname, lname, age, email, password, avatar, gender) { this.fname = fname; this.lname = lname; this.age = age; this.email = email; this.password = password; this.avatar = avatar; this.gender = gender; }

 /* Methods */
 createUser() {
     db.insertUser({
         'firstName'     : this.fname,
         'lastName'      : this.lname,
         'age'           : this.age,
         'email'         : this.email,
         'password'      : this.password,
         'userAvatar'    : this.avatar,
         'gender'        : this.gender
     })
     .then(() => {
         console.log(this);
         return this;
     })
     .catch(error => {
         if (error.code == 'ER_DUP_ENTRY' && error.errno === 1062) throw new Error('This email is allready in use')
         else throw error;
     })
 }

 /* Validations */

}

module.exports = User;

Controller

const newUser = new User("fname", "lname", 22, "ema2121il", "password", "avatar", "gender"); newUser.createUser(); res.send(newUser)

I need to find a way to pass the validations errors, or the duplicate error from the point 2 (Object class) to the controller.

Please how can I do this?

Currently, I cannot send the rejected response from the User class to the express response — daniel sas
– daniel sas, Commented Jan 20, 2022 at 18:26
the validation should be done in controller. i recommend joi library — Mojo Allmighty
– Mojo Allmighty, Commented Jan 20, 2022 at 18:39

Robo Rick · Accepted Answer · 2022-01-20 18:41:55Z

1

So, if your goal is to return data to the express controller (from the class). The best way is to utilize the Promise Library. So your createUser function should look like this:

 createUser() {
   return new Promise ((resolve, reject) =>  {
       db.insertUser({
         'firstName'     : this.fname,
         'lastName'      : this.lname,
         'age'           : this.age,
         'email'         : this.email,
         'password'      : this.password,
         'userAvatar'    : this.avatar,
         'gender'        : this.gender
       })
       .then(() => {
         console.log(this);
         this.runValidations()
         return resolve(this);
     })
     .catch(error => {
         if (error.code == 'ER_DUP_ENTRY' && error.errno === 1062) {
            return reject('This email is already in use')
         } else {
            return reject();
          } 
     })
   });
 }

Then to utilize it from your controller, utilize async/await to utilize the method.

//The Controller Code

app.get('/create-user', async(req, res) =>  {
    const user = new User(req.body) // Assuming this is how you're instantiating class
    try {
       const newUser = await user.createUser();
       console.log("User is Created");
    } catch (err) {
       //Your Error will be available here.
       console.log("Your Error: ", err)
    }
    

})

This should get you what you need :)

answered Jan 20, 2022 at 18:41

Robo Rick

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1 Comment

daniel sas Over a year ago

This is perfect. Thanks aloooot. :)

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